Inventor Rotations

Inventor Rotations

Post by Mark Beattys Dobbr » Sun, 28 Aug 1994 06:20:51



Greetings -

        I'm trying to convert Inventor axis,angle rotations to
x-angle,y-angle,z-angle form. Does anyone have an algorithm handy
or know of a good reference?

Mark

 
 
 

Inventor Rotations

Post by Gavin Be » Sun, 28 Aug 1994 14:49:38




Quote:>    I'm trying to convert Inventor axis,angle rotations to
>x-angle,y-angle,z-angle form. Does anyone have an algorithm handy
>or know of a good reference?

Graphics Gems IV (or maybe 3 or 2 or 1, but I think it is 4...) has a
great article on converting quaternions (the representation Inventor
uses) to Euler angles (x-angle, y-angle, z-angle is one particular set
of Euler angles) by Ken Shoemake.

(Don't you just hate people who use too many parentheses)
--

Inventor on the www:  http://www.sgi.com/tech/Inventor.html

 
 
 

Inventor Rotations

Post by Bruce Tenna » Thu, 01 Sep 1994 23:15:12


Quick question dealing with quaternions verse Euler(angles or paramters)...

What are the major advantages/disadvantages to it?  We use Euler Parameters
in our routines for dynamics calculations... Is there an advantage graphically
to useing one or the other?

I have very basic knowledge of Eulor and almost none of quaternions(just that
Eulor parameters are normalized quaternions)...

Anyway just curious here...  no Biggie

 
 
 

Inventor Rotations

Post by Bruce Tenna » Thu, 01 Sep 1994 23:49:38


I have a question.  What I need is some direction or tips to speed up an
inventor scene(OpenInventor, Indigo r4000 not sure gfx, but not 8-bit).

Here's sort of the basic scene..  Its a SoSeperator with 12 children, 11
of the children are SoShapeKit-Nurbs, and the other is a SoShapeKit-Sphere.

I know NURBS in general(or it sure seems it) are slower than most other forms
but is there any good hints as to ways to speed the rendering up?  I'm
animating the scene and need the rendering to be quick.  Right now I think I
get somwhere in the area of 1 render per second...  I would like 15/sec but
would settle with 5/sec or so...  All the nurbs are revolved shapes...(its a
bowling alley basically).

Also, something that always bugs me...  Is there a way to make callbacks wait
until the SoXtViewer is done drawiong its window and buttons and such before
it attampts to start animating?  I just usually miss the first 5-10 frames
because of this..

Bruce Tennant
Chace and Associates Engineering

 
 
 

Inventor Rotations

Post by Gavin Be » Fri, 02 Sep 1994 01:50:33


Quote:>Quick question dealing with quaternions verse Euler(angles or paramters)...

>What are the major advantages/disadvantages to it?  We use Euler Parameters
>in our routines for dynamics calculations... Is there an advantage graphically
>to useing one or the other?

Euler paramaters == quaternions used for orientations == unit quaternions

Euler angles are three independent axes used to specify an orientation
(e.g. yaw-pitch-roll or X-Y-Z).

Quaternions/Euler paramaters are:
  -- very easy to convert to a rotation matrix
  -- are fairly easy to interpolate
  -- never suffer 'gimble lock'

The only advantages I can think of for Euler angles are:
  -- they use up less storage (3 floats instead of 4)
  -- they match how some users think of orientation

--

Inventor on the www:  http://www.sgi.com/tech/Inventor.html

 
 
 

1. Inventor rotations into Euler angles

Hi,
        Inventor's SbRotation uses standard quaternion representation. So you can
directly convert it to euler angles by using the standard formulae. For more
details refer to the paper titled "Animating Rotation with Quaternion Curves"
by Ken Shoemake, ACM Siggraph 85.

best

- Ashish
--
------------------------------------------------------------------------------
Ashish Kolli, Carnegie Mellon University

WWW   :         http://www.cs.cmu.edu/afs/cs/user/ashishk/www/self.html
------------------------------------------------------------------------------

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